You can use a polarized cap. I think our boards were missing the polarity mark or something, so we supplied a bi-polar cap to help prevent mistakes. To be honest, I can't remember exactly, but it was something like that.
Assesears said:
btw - Bruce - what exact schematic you use ........... I misplaced it somehow .......
😉
Assesears said:
presuming that you use BL variant of 2SK170 ......... that's good one
I think that you can expect further improvement with little BC instead IRFs ;
you didn't must search for BC critters ( I have impression that they are somewhat easier to buy in Europe than in US ) - you can use there any decent little one bjt with similar UIP characteristics .
I use them from same reason Papa use ZTX ......... they dirt cheap , available almiost in every tobacco store and its just fuss buying them in lesser quantity than ,say, 300pcs - even for DIY purposes
later just add output stage
........ and you don't need F4 at all ........... 
Yes I used the BL one, not matched just had them in the spares bin threw them in and listened, the BC's I have plenty of used for a clock in a cd player some time ago if I remember easy to get hold of as well in large amounts. Rather than just going for it with your mods I'll go one step at a time and just listen. Mind you also tempted by your Pumpkin.
All these projects so little time lol.
Bruce
All these projects so little time lol.
Bruce
Hi Bruce,
what power-amp do you connect your X-BOSOZ to?
The high output impedance could lead to significant changes in frequency responce.
I noticed you have a gain of 10x. Is the open loop gain high enough for this?
William
what power-amp do you connect your X-BOSOZ to?
The high output impedance could lead to significant changes in frequency responce.
I noticed you have a gain of 10x. Is the open loop gain high enough for this?
William
Hi,
Power amps used A30,Mini A, Chip amp, ESP P3 - playing with the mini at the moment, can't remember what gain running at the moment depending on what amp I'm running, once the F4 is finished will have to increase. All these changes the boards are getting abit abused now.
Will make an off board one day with various gain settings to cover most amps I have using say dip switches.
Frequency response have noticed changes not run any measurements as use my ears mostly, run FR speakers my top end hearing is starting to go though.
Ta
Bruce
not figured out how you put the quotes in yet should learn.
Power amps used A30,Mini A, Chip amp, ESP P3 - playing with the mini at the moment, can't remember what gain running at the moment depending on what amp I'm running, once the F4 is finished will have to increase. All these changes the boards are getting abit abused now.
Will make an off board one day with various gain settings to cover most amps I have using say dip switches.
Frequency response have noticed changes not run any measurements as use my ears mostly, run FR speakers my top end hearing is starting to go though.
Ta
Bruce
not figured out how you put the quotes in yet should learn.
Humm with X-BOSOZ
Ah! finally some peace and no hum.
Thought I would share this, my twisted X-BOSOZ has always sounded excellent but was plagued with a hum. I figured I would attack it when I upgraded to the Uber controller (Joshua tree and Darwin) but the boys at Twisted have been a little slow (hint ,hint) and that dratted hum finally got to me. I came to find out it was coming from the controller wires going to the Darwin routed to close to the power transformer. It was especially irritating when I was listening to my Pearl phone preamp because I have to turn the volume up due to its lack of gain.I guess I will have to bite the bullet and buy their twisted X pre to convert Pearl to Balanced and bump the gain a little. I am in the process of building a pair of F4s and will be bumping gain on X_BOSOZ preamp. I noticed in Chocky's fet upgrade it looked like R18 and R19 are 100K but R5 and R8 were changed as well, is the net result still an increase in the gain enough to drive the F4?
Thanks
Bill
Ah! finally some peace and no hum.
Thought I would share this, my twisted X-BOSOZ has always sounded excellent but was plagued with a hum. I figured I would attack it when I upgraded to the Uber controller (Joshua tree and Darwin) but the boys at Twisted have been a little slow (hint ,hint) and that dratted hum finally got to me. I came to find out it was coming from the controller wires going to the Darwin routed to close to the power transformer. It was especially irritating when I was listening to my Pearl phone preamp because I have to turn the volume up due to its lack of gain.I guess I will have to bite the bullet and buy their twisted X pre to convert Pearl to Balanced and bump the gain a little. I am in the process of building a pair of F4s and will be bumping gain on X_BOSOZ preamp. I noticed in Chocky's fet upgrade it looked like R18 and R19 are 100K but R5 and R8 were changed as well, is the net result still an increase in the gain enough to drive the F4?
Thanks
Bill
Re: Humm with X-BOSOZ
yup ..... ratio of these resistors is gain
EDIT:
dunno ,in fact, - gimme exact schematic .......... I'm kinda lost in guessing ......... who knows which resistor .......
wirewiggler said:
yup ..... ratio of these resistors is gain
EDIT:
dunno ,in fact, - gimme exact schematic .......... I'm kinda lost in guessing ......... who knows which resistor .......
Re: X-BOSOZ Fet upgrade
on twisted schm ratio of R19/R14 (R18/R15) is what you have for gain
wirewiggler said:
on twisted schm ratio of R19/R14 (R18/R15) is what you have for gain
Re: Re: X-BOSOZ Fet upgrade
For the R5 & R8 is not for the gain.
I found that R5 is changed from 10K to 221, and R8 from 50 ohm plot to 27 !
Which one is correct and why ?
Thanks !
Zen Mod said:
For the R5 & R8 is not for the gain.
I found that R5 is changed from 10K to 221, and R8 from 50 ohm plot to 27 !
Which one is correct and why ?
Thanks !
Member
Joined 2002
Any one looking for a pre-amp, im selling my X-BOSOZ, it comes with case and relay volume pot inside, ready to use.
Jase
Jase
I was wondering if someone can help me with a problem I've run into.
I had built the Twisted Pear BoSoZ, and all worked well. I finally finished the case and in/out selector and controller, but now I have a problem on one of the 2 boards.
Basically, R2 and R7 start burning up, while R1 and R6 stay warm. I measured the voltages at different points, and the odd thing is that I get a much too great voltage drop after R2/R7. I get 75.3V before them, and 7.5V after (as noted on the attached schematic). the 7.5V decreases slowly as time passes. I also took the board out and tried it without having the FETs attached to the case, but I still have the same issue, therefore it doesn't seem like it's a short on the FETs' drains.
I read in other threads, and one of Zen Mod's drawings indicates that I should have a current of about 50mA on that branch, but I get a draw of about 90mA. Can it be that I damaged the FETs (Q2/Q4)?
Paul
I had built the Twisted Pear BoSoZ, and all worked well. I finally finished the case and in/out selector and controller, but now I have a problem on one of the 2 boards.
Basically, R2 and R7 start burning up, while R1 and R6 stay warm. I measured the voltages at different points, and the odd thing is that I get a much too great voltage drop after R2/R7. I get 75.3V before them, and 7.5V after (as noted on the attached schematic). the 7.5V decreases slowly as time passes. I also took the board out and tried it without having the FETs attached to the case, but I still have the same issue, therefore it doesn't seem like it's a short on the FETs' drains.
I read in other threads, and one of Zen Mod's drawings indicates that I should have a current of about 50mA on that branch, but I get a draw of about 90mA. Can it be that I damaged the FETs (Q2/Q4)?
Paul
